Removing nickel carbonyl from crude propionic acid

ABSTRACT

AN IMPROVED PROCESS FOR THE REMOVAL OF NICKEL CARBONYL FROM CRUDE PROPIONIC ACID CONTAINING IT (WHICH HAS BEEN OBTAINED BY REACTING OF EHTYLENE WITH CARBON MONOXIDE AND WATER IN THE PRESENCE OF NICKEL CARBONYL) BY TREATMENT WITH A GAS CONTAINING OXYGEN, THE IMPROVEMENT COMPRISING CARRYING OUT THE TREATMENT COUNTERCURRENT IN A TRICKLING PHASE AND USING 5 TO 20 M. 3 OF THE INERT GAS CONTAINING 3 TO 10% BY VOLUME OF OXYGEN PER M.3 OF CRUDE PROPIONIC ACID CONTAINING MICKEL CARBONYL. PROPIONIC ACID IS USED FOR THE PRODUCTION OF PROPIONIC ESTERS AND FOR THE TREATMENT OF FEEDSTUFFS.

United States Patent 3,743,674 REMOVING NICKEL CARBONYL FROM CRUDE PROPIONIC ACID Heinz Hohenschutz, Mannheim, and Paul Hornberger and Horst Buelow, Ludwigshafen, Germany, assignors to Badisehe Anilin- 8: Soda-Fabrik Aktiengesellschaft, Ludwigshafen am Rhine, Germany No Drawing. Filed June 30, 1972, Ser. No. 267,986 Int. Cl. C07c 51/14, 51/42 US. Cl. 260-540 4 Claims ABSTRACT OF THE DISCLOSURE An improved process for the removal of nickel carbonyl from crude propionic acid containing it (which has been obtained by reacting of ethylene with carbon monoxide and water in the presence of nickel carbonyl) by treatment with a gas containing oxygen, the improvement comprising carrying out the treatment countercurrent in a trickling phase and using 5 to 20 m. of the inert gas containing 3 to by volume of oxygen per m3 of crude propionic acid containing nickel carbonyl. Propionic acid is used for the production of propionic esters and for the treatment of feedstutls.

This invention relates to a process for the removal of nickel carbonyl from crude propionic acid containing the same (which has been obtained by reaction of ethylene with carbon monoxide and water in the presence of nickel carbonyl) by treatment with gases.

A process is known according to which metal carbonyls contained in carbonylation products are decomposed therefrom by treatment with a mixture of hydrogen and carbon monoxide at elevated temperature. According to another process disclosed in German patent specification No. 1,014,093 the reaction mixture obtained in the pro duction of propionic acid is relieved of pressure and the whole of the nickel carbonyl thereby decomposed. Both of these methods have the disadvantage that deposits form on the walls of the vessel by decomposition of the metal carbonyls. Moreover, it is very expensive to separate the finely dispersed metal sludge. According to other methods disclosed in US. Pat. 2,547,178 and German printed application No. 1,107,212 metal carbonyls contained in carbonylation products are completely oxidized by treatment with gas containing oxygen. Apart from the fact that care has to be taken that the oxidation of the metal carbonyls is complete so as to avoid injurious effects in later treatments, the metal salts obtained have to be recovered and worked up so that they may be reused for carbonylation. The use of metal salts in the carbonylation always has the disadvantage however that a certain inhibition occurs until the metal carbonyls have been reformed. Finally it is known from German Pat. 1,279,667 that the removal of metal carbonyls can be carried out by treatment with gas containing oxygen in the presence of an acid medium and substances having a large surface. This method not only has the abovementioned disadvantages but also the additional disadvantage that the active surface very rapidly becomes inactive because of the high boiling point byproducts contained in the carbonylation products.

It is an object of the invention to provide a process in which nickel carbonyl is removed from crude propionic acid containing it, metal deposits on the apparatus are avoided and nickel carbonyl is recovered as such.

In accordance with this invention this and other objects and advantages are achieved in an improved process for removing nickel carbonyl from crude propionic acid containing it (which has been obtained by reaction of ethylene with carbon monoxide and water in the presence "ice of nickel carbonyl) by treatment with a gas containing oxygen in which the improvement consists in carrying out the treatment in a countercurrent trickling phase and using from 5 to 20 m. of an inert gas which contains from 3 to 10% by volume of oxygen per m. of crude propionic acid containing nickel carbonyl.

The new process is notable in that it would have been expected that in the treatment of crude propionic acid containing nickel carbonyl with gas containing molecular oxygen the nickel carbonyl-as in prior methods-would have been completely oxidized and the corresponding nickel salts would have been obtained.

The crude propionic acid is prepared by reaction of ethylene with carbon monoxide and water in the presence of nickel carbonyl. Ethylene and carbon monoxide are generally used in a molar ratio of from 1:08 to 1:2, particularly in a molar ratio of from 1:1 to 1:15. It is also advantageous to use from 1.5 to 2.5 moles of water for each mole of ethylene. Nickel carbonyl is used as catalyst in an amount of from 0.5 to 3% by weight calculated as metallic nickel and based on ethylene. The reaction is generally carried out at a temperature of 250 to 320 C., particularly from 270 to 300 C. Moreover it is advantageous to use pressures of from 100 to 300, particularly from 200 to 250, atmospheres.

Crude propionic acid prepared in this way generally contains from to by weight of propionic acid, from 8 to 16% by weight of water, from 0.3 to 0.7% by weight of nickel propionate, from 0.2 to 0.4% by weight of nickel carbonyl and also from 0.6 to 1% by weight of dissolved gas such as ethane, ethylene, carbon monoxide and carbon dioxide, in addition to up to 0.7% by weight of high boiling point constituents.

The crude propionic acid containing nickel carbonyl is treated per m. with from 5 to 20 m preferably from 8 to 15 m. of inert gas which contains from 3 to 10%, particularly from 4 to 7%, by volume of molecular oxygen. Examples of suitable inert gases are nitrogen, carbon dioxide and carbon monoxide. it is also advantageous to use offgas from the production of propionic acid such as is obtained after removing the nickel carbonyl. It contains for example 4.2% by volume of ethylene, 45.9% by volume of carbon monoxide, 10.8% by volume of carbon dioxide and up to 39.1% by volume of other inert substances such as nitrogen.

Treatment is carried out countercurrent in trickling phase. Advantageously the propionic acid containing nickel carbonyl is fed in at the top of a column which advantageously is packed, for example with Raschig rings or Pall rings, to ensure good mixing and the said gas mixture is fed in at the bottom. The treatment is generally carried out at a temperature of from 0 to 200 C., particularly at temperatures of from 50 to C. Atmospheric pressure or superatmospheric pressure up to 10 atmospheres gauge is generally used.

Propionic acid produced according to the process of the invention is suitable for the production of esters or for the treatment of feedstufls.

The process according to the invention is illustrated in the following examples.

EXAMPLE 1 3804 kg. per hour of crude propionic acid of the composition shown in the table below (obtained in the synthesis of propionic acid after relieving the product from pressure and separating the offgas) is supplied to the top of a stainless steel column having a diameter of 300 mm. and a length of 12 meters which is packed with Pall rings. 40 cubic meters (STP) per hour of a mixture of 30 m5 of nitrogen and 10 m. of air is passed into the bottoms of the column. The temperature in the bottoms of the column is 80 C. and at the top 78 C. Pressure varies from 0.6 to 1 atmosphere gauge. The results obtained may be seen in the following table.

Dis- Fresh Feed charge gas Ofigas Propionic acid 3, 252. 2 Water 465. 6 Nickel propionate Nickel carbonyl Total 3, 804. 3, 751. 8 50. 3 102.

No appreciable deposits of metallic nickel can be detected in the column after a running period of six months.

EXAMPLE 2 The procedure described in Example 1 is followed but only 40 m. of nitrogen is used. After from one month to three months the deposits of nickel are so extensive that the plant has to be shut down and cleaned.

We claim:

1. An improved process for the removal of nickel carbonyl from crude propionic acid containing it, said acid having been obtained by reaction of ethylene with carbon monoxide and water in the presence of nickel carbonyl, by treatment with a gas containing oxygen wherein the improvement comprises carrying out the treatment countercurrent in a trickling phase at 0-200 C. and at a pressure of 1-10 atmospheres and using from 5 to 20 m. of inert gas containing from 3 to by 'volume of oxygen for each m. of crude propionic acid containing nickel carbonyl.

2. A process as claimed in claim 1 wherein from 8 to m. of inert gas containing from 4 to 7% by volume of oxygen is used per 111. of crude propionic acid containing nickel carbonyl.

3. A process as claimed in claim 1 wherein the treatment is carried out at a temperature of from to C.

4. A process as claimed in claim 1 wherein the treatment is carried out at atmospheric pressure.

References Cited UNITED STATES PATENTS 2,547,178 4/1951 Spence 260-439 R 2,878,258 3/1959 Pistor 26054O VIVIAN GARNER, Primary Examiner U.S. Cl. X.R.

Egg? TJNTTED STATES PATENT oTTToE QE'NWCATE Ci CCRRECTION Dated 5:

Patent No.

Inventofls) Heinz Hohenschutz et al It is certifie that error appears in the above-identified patent amfi that said Letters Patent are hereby corrected as shown below:

Column 1, line 9, insert Claims priority, application Germany, July 12, 1971, P 21 5 684.9

Column 5, in 'the table, under "Offgas"; "102. should read 102.5

Signed and sealed this 15th day of January 197E.

(SEAL) Attest:

EDWARD M.FLETGEER; JR Attesting Officer RENE D. TEGTME'YER Acting Commissioner of Patents 

